Safety



PATENTED JAN. 12, 1904.

H. G. WRIGHT.

SAFETY APPLIANCE SYSTEM FOR ELEGTRIGALLY AGTUATED ELEVATORS.

APPLIOATION FILED MAY 9,1903.

4 SHEETS-SHEET 1.

N0 MODEL.

Inventor Zgk+ Attorne I I F .3. 1

Witnesses Z PATENTED JAN. 12, 1904.

H. G. WRIGHT. SAFETY APPLIANCE SYSTEM FOR ELEGTRIOALLY ACTUATEDELEVATORS.

APPLICATION FILED MAY 9, 1903. N0 MODEL. 4.SHEETSSHEET 2.

Witnesses Inventor Hm 72 M Attorney PATENTED JAN. 12, 1904.

H. G. WRIGHT. SAFETY APPLIANCE SYSTEM FOR BLEGTRIGALLY AGTUATEDELEVATORS.

APPLICATION FILED MAY 9. 1903. N0 MODEL. 4 SHEETSSHEET 3.

\nvenoor Witnesses rag'ial t Attorn ey PATENTED JAN. 12, 1904.

H. G. WRIGHT. SAFETY APPLIANCE SYSTEM FOR ELEGTRIGALLY AOTUATEDELEVATORS.

APPLICATION FILED MAY 9. 1903.

4 SHEETS-SHEET 4.

N0 MODEL.

Witnesses UNITED STATES Patented January 12, 1904.

PATENT OFFICE.

HARRY G. WRIGHT, OF PROVIDENCE, RHODE ISLAND, ASSIGNOR TO WILLIAM C.WOODWARD, OF PROVIDENCE, RHODE ISLAND.

SAFETY-APPLIANCE SYSTEM FOR ELECTRlCALLY-ACTUATED ELEVAT0RS.

SPECIFICATIONforming part of Letters Patent No. 749,416, dated January12, 1904.

Application filed May 9, 1903. Serial NO- 156,415. (N0 11101161.)

pliance system or construction for electricallyaetuated elevators, theinvention being of the type :or class adapted to automatically preventthe car from moving in case any of the landing-doors are not fullyclosed or in case the normal working of the elevator is interrupted.

In electric safety appliances or systems for electrically-propelledelevators heretofore devised it has been usual, so far as I am aware, toconnect the same to some part of the motor or mechanism which actuatesand controls the movements ofthe elevator-car. In some in stances thecar itself carriessome portion of the safety device, the same beingconnected to the manipulating. cord or lever, through which latter theoperator is enabled to normally control the cars movements. The electriccurrents employed for energizing orrendering operative such formersafety appliances were usually taken from that of electric-lightingsystems or some other source independent of that employed for operatingthe hoisting mechanism or motorwhich propelled the car. In former safetydevices, or at least some of them, the construction and arrangement weresuch that themain drivingv or hoisting mechanism was stopped or renderedinoperative whenever the safety appliance was brought into action.

' In another form of electrically-operated elevatorsthe drivingmechanism thereof .eomprises a pair of electric motors the field-coilsof which are in series and. permanently connected, the armatures beingcapable of continuous-rotation, but running :in'fopposite directions. Asuitable-Iconductor connects the Y fields and extends to thelever-contact of a resistance-box mounted inf-thejcar. By throwing thislever one way or the other from the center of its arc of travel ashunt-circuit of variable resistance may be closed in parallel with thefield-circuit of one or the other of the motors, thus weakeningv thefield and varying the speed of the corresponding armature.

With the operating-lever moved to one or the other extreme of the arcthe car is moving, up or down, as the case may be, at maximum speed,while with the lever in the center position the two field strengths areequal and the armature revolves in unison or at equal speeds, the carthen stopping. It may be added that the car is supportedby cablespassing over a top sheave, the opposite end of the cables being securedto a movable counterweight, carrying a sheave onwhich is mounted anendless cable,

. the latter passing downwardly and around the two motors pulleys andalso around a sheave carried in a movable tension-frame, the latterbeingsupported by a cable extending upwardly over a sheave and securedto the counterweight. The tension-frame and car always move in a.direction opposed to that of the counterweight. Anobjection to suchformer electrically-controlled safety appliances or gate-locks ofpassenger-elevators is that in cases where the safeties are'madeoperative by means of an independent electric circuit it is possiblethat the latter may become accidentally inoperative and unknown to theattendant, .in which event it is clear that the cars movements are notthen governed in any manner whatever by the presence of the safetyattachment. ,Oonsequently accidents to the passengers might happeneventhough the operator exercises a great degree of care. In my inventionthe electric current, employed for the door or gate locks ispreferablytaken from the main power-circuit that supplies the currentwhich operates the motors. The current for operating said safetyattachment is, however, tapped or taken from the main cur rent beforethe latter passes tothe motors. Thus it is clear that even though themotors themselves should become inoperative or dead the currentcommunicating with the safety device will still remain operative.

In the drawings I have indicated one class of electrically-propelledelevators, the same being provided with a series of suitably-arrangedswitches, magnets, resistances,conductors, '&c., and physically situatedor located between the motor and the source of supply of electriccurrent. In the car itself is mounted a variable resistance electricallyconnected to said switches, &c. By means of the lever-contact member ofsaid variable resistance the operator is enabled to normally control thecars movements up or down, as desired. These features, however, Idisclaim as my invention, but are introduced more especially torepresent the adaptability of my improved safety device thereto. Thislatter includes what I term a master-switch, the same being capable ofcarrying the entire current of the controlling-circuit and also beingelectrically connected to some of the said switches, conductors, &c.(forming branch circuits) of the main electric circuit. It is alsoelectrically connected to a series of door or gate locks located in abranch or subsidiary circuit. The primary object of the last-namedcircuit and its door-locks is to provide safety means (wholly automaticin action and disconnected from the car) capable of positivelypreventing the car from starting or moving when any of the landing-doorsare not fully closed. The master-switch is connected to thebrake-circuit of the car and also to the circuit, in which are locatedrheostats for controlling the motors speed. The main switch of thelastnamed circuit is kept normally closed, thereby adapting the motorsto run continuously. The current for the door-lock circuit is preferablytaken from the electric circuit at a point between the main switch andthe motor. The resistance of the door-lock circuit is lower than that ofthe circuit in which the magnet of the master-switch is located, and themagnet of the latter is connected in shunt to the door-lock circuit, theconstruction being such that the magnet-coil offers a greater resistanceto the passage of the current through it than through the more directand lesser resistance of the circuit controlling the doorlocks.Consequently the other circuits controlled by the master-switch are keptnormally closed or operative when all the doors or gates of thedoor-lock circuit are fully closed, the car itself then being movable,as hereinafter explained. When, .however, a landing-door is opened tosuch an extent that the door-lock circuit is thereby broken, the currentthen is shunted through the magnet-coil of the master-switch andenergizes it, the result being to actuate said switch and open the othercircuits connected with and controlled by it.- In this position of theswitch the car. is immovable, and the operator in the car cannotpossibly actuate it until the door-lock circuit is again made operativebyclosing the landing door, at which instant, too, the magnet of themaster-switch becomes demagnetized and permits its mechanism toautomatically close or reestablish the other circuits controlled by it,the car then being in the operative condition.

In the four accompanying sheets of drawings illustrating my inventionand also indicating the manner of its relation and connection to anelectric circuit arranged to propel or actuate the mechanism of apassenger-elevator, Figure 1 is a front view of the mechanical andelectrical device or master-switch, as it may be called, the relation ofthe parts being in the normal operative position and corresponding withthe position of the door-lock shown in Fig. 5. Fig. 2 is a verticaltransverse section taken on line 2 2 of Fig. 1. Fig. 3 is a diagrammaticrepresentation of the wiring, &c., corresponding with Fig. 1. Fig. 4 isa front elevation, in partial section, of the improvedelectrically-connected door-lock or switch, the door being closed. Inthis position the car may be normally operated. Fig. 5 is a similarview, the door being open or disengaged from the switch. In thisposition the electric circuit of the door locks is automatically broken,thereby through the medium of suitable connections rendering thecarcontrolling mechanism temporarily inoperative. Fig. 1 shows acorresponding position of the master-switch. Fig. 6 is a planview of thelock. Fig. 7 is a side elevation of it corresponding with Fig. 4. Fig. 8is a front elevation, in reduced scale, showing a series oflanding-doors of an elevator system provided with my improved door-locksand also indicating diagrammatically a passenger-car, electric motorsfor operating the car, electric circuits connected with the car andmotors, and the master-switch in electrical connection with saidcircuits and with the several door-locks. Fig.9 is a sectional View, inenlarged scale, of the'automatic switch 3, taken on line .2 2 of Fig. 8;and Fig. 10 is a front view, in re duced scale, showing diagrammaticallythe master-switch located in the main circuit and shunt-connected to thedoor-lock circuit. In this arrangement the electric motor is adapted tostop whenever it is desired to stop the car at any of thelanding-floors.

In Fig. 8 of the drawings I have indicated diagrammatically one form ortype of electric-elevator systems substantially as heretofore producedand used and hereinbefore referred to. Said drawing also representsadditionally a series of door-locks H, electrically connected to one ofthe controlling-circuits of the elevator and to the master-switch A.This latter, which is shunt-connected to other electric circuits of thesystem, constitutes an essential part of my present invention.

I would state briefly that the power-circuit or main electric circuit isconducted to a pair of electric motors M M, in which the field'- coilsare arranged in series and permanently connected. The car C is adaptedto be electrically propelled by cables and mechanism (not shown) in anysuitable manner. The electric current may be first taken from apower-circuit through a manually-controlled switch or circuitsbreaker,(indicated at 1.) From the latter by means of suitable conductors thecurrent passes to a manuallycontrolled variable resistance D andlevercontact D, mounted in the car. An automatic switch,(indicated at 2)may be located in the motor-circuit, said switch being so connectedand'arranged that the movements of the car are controlled by theoperator through the medium of the lever D. Now in order to start themotors the operator closes the two switches a '0' in the car, whichaction through proper connections energizes a magnet at back of saidswitch 2 and closes the latter, thereby slowly starting the motors. Thecurrent of the motors armatures passes through a series coil on thefields, the result being to increasethe motors speed up to the normal.When this takes place, the series coil is cut outautomatically by aseries of magnets m mi m m", which lift their corresponding diskssuccessively, thereby imparting suflicient current to a magnet m at theback of the automatic switch 3 toaclose the latter. Now to operate thecar the leverD is moved in the desired directionsay to the right indescending and to the left in ascending the several landing-doors (Zthen being closed and the corresponding circuit short-circuited throughthe door-locks H. In the event of a door being opened toany extent whilethe car is moving the latter will stop instantly, al-

though the motors may be continued in action.

This result is .due to the fact that the thusopen door circuit thenshunts the current through the magnet-coil of the master-switch. whichlatter thereby elevates the contact-point from the mercury-cups, thusopening the main controlling-circuits and the brake-circuit connectedtherewith. The motor is stopped by simply opening the two switches 4;,thereby demagnetizing the magnets of said switches 52 and 3, whichlatter then automatically drop and open the corresponding circuits in awell-known manner.

The=masterswitch A may be provided with aseries of manually-controlledcut-outs, as s s s s 'sflsubstantially-as indicated in Figs. 1, 3, andv8. These as well as other parts of the switch are preferably secured toa small conveniently-located switchboard f, the whole being inclosed ina suitable protecting box or casing f, having a locked glass door orcover f The master-switch'A consists, essentially, of two pairs ofindependent mercury contactcups 0 a and a a, interposed in twoindependent circuits, adapted to control the elevators I movements,secured to and insulated from a bracket or base member 6, of marble orother proper insulating material. The cups are or suitable insulation.They are adapted to contain a quantity of mercury 0, the surface levelof which is substantially uniformin all. I prefer to use suitable oil 0on top of the mercury, thus forming a fluid seal. The oil also serves togreatly lessen and stifle the are when the switch is being opened.Directly above the mercury-cups is located a vertical]y-arrangedelectromagnet-coil c, the spool of which is wound with sufficientconducting-wire to form the desired resistance of the coil. Anon-revoluble core or rod 0' is mounted to move freely in a verticalendwise direction centrally of the coil, the rod rising upwardlywhenvthe magnet is energized and falling by gravity when the electriccircuit of the coil is shunted by the lower resistance of thecloseddoor-lock circuit. .To the lower portion of said rod are secured apair of horizontal crossed conductor-bars a afhaving contact-pins a, ofstecl or other material unaffected by mercury, dedepending from theirouter or free ends, as clearly shown in Figs. 1 and 2. The said bars arethoroughlyinsulated from each .other and from the core 0, the four pinsthereof being arranged centrally of the four corresponding mercury-cups.By means of an exterior nut or adjustable stop 0 of the red the degreeof mercury contact with the pins may bereadily controlled as desired.

, As drawn, (see Fig. 8,) the mercury-cups a are connected by suitableconductors at, to the brake-circuit of the elevator system, the cups (0being connected by suitable conductors a a to the controller-circuit.These circuits being exterior to the master-switch and the manner oftheir construction, aswell as mechanical devices (not shown) connectedtherewith and with the car, form no part of my invention, except asbeing combined with or arranged to coact with the master-switch A. Imaystate that in an electrically actuated and controlled elevator the.controller-circuit, so called, is connected tocertain devices adaptedto regulate or control the current which propels the car. Thebrake-circuit of such form of elevators is usually arranged so nectedfrom the brake-wheel; but when thecircuit is broken said jaws (by meansof the springs) clamp the wheel or brake device to prevent the car fromfurther movement.- Thus it is obvious that when the conductor-bars aredropped the pins 0 thereof will form electrically-closed contacts withthe mercury-cups, the latter, as just stated, being located in the brakeand controller circuits. The circuits are opened by elevating the bars,thereby withdrawing the pins from the mercury. I prefer to have thecontact-pins of the bar a (of the brake-circuit) extend below, those ofthe other or controller-circuit. As thus constructed and arranged, it isclear that the lat may be covered on their outer surface with l tercircuit will become open or dead slightly in advance of thebrake-circuit whenever the magnet 0 is sufi iciently energized toelevate the bars, &c., to the position represented in Figs. 1 and 2. Ideem this an important feature of my invention.

The door or,gate lock proper, H, Figs. tto 7, has a frame or housingsecured to the doorcasing in a suitable manner and at any convenientpoint say near the top of the door. In the said lock-frame are mountedtwo independently insulated vertically-movable springpressed pins orbolts 72, It, each provided at its upper end with an adjustablecurrent-conductingstop-collar in sliding contact with a combined guideand conductor plate 72. A swinging contact-lever Z is located contiguousto the lower portion of said bolts. Its outer or-free end carries a pairof current-conductingpins orhammers W. Z, insulated from the lever, butunited by-the conductor The upper ends of the pins are adapted to engagethe lower ends of the bolts. As drawn, the latter aregroovedtransversely, the ends of the corresponding pins having a counterpartform, thus while the lever is being swung upwardly insuring a morecomplete and perfect contact of the pins with the yielding bolts.

The landing-door (Z has a projecting dog or bolt CZ secured thereto,arranged to pass through an opening (Z of the door-frame and engage.theadjacent or rear side (Z of said contact-lever Z, thereby whenclosing the door forcing the pins Z a" upwardly into yielding contactwith the bolts it it. Fig. 4 represents the normal position of the partswhen the door is fully closed, the collars h then being in engagementwith the poles orrconductors p p and plates 70 0f the branch circuitcommunicating by means of conducting-wires 2' r with the master-switchA. (See also Figs. 8 and 9.)

The electric current for the circuit which operates the door-locks H isor may be taken from an automatic switch 3, Figs. 8 and 9, in electricalcontact with posts f0, connected in turn to the conductor-terminals ofthe locks by said wires '2' 0' These latter are connected in shunt toclosed switches (later described) 8' ,s, respectively, and from which byconductors r r the current is led to and from the magnet 0 of themaster-switch.

Referring to Fig. 9, it will be seen that the lower portion of thecontact-bar m of the automatic switch 3 is extended and carries atransverse contact member (1: normally disconnected from thespring-pressed posts (0. At the instant, however, the switch opens (seedotted lines)the said contact member 0 will engage the yielding posts:0, thereby at the same instant closing the door-lock circuit connectedtherewith. The resistance of the doorlocks circuit is much less than theresistance of the magnetcoils circuit. Therefore as these circuits areconnected in shunt one to the other when the door-lock circnlt s closedthe greater part of the current will pass through it rather than throughthe higher resistance of the magnet-coil (0) circuit, the latter thenbeing practically demagnetized and having the pins 0 of the contact-barsin engagement with the mercury of the respective cups, therebypermitting the currents which control the elevators movements to actnormally. I may add that when the car is at either extreme of movement,top or bottom, the m0- tor stops, but is in continuous operation whilethe car stops at any of the intermediate floors. Upon stopping theelevator-car and opening the corresponding landing door, therebydisengaging the bolt J from the contact-leverZ of the door-lock, thesprings it of the spring-pressed bolts force the latter downwardly untilarrested by the stops 762, the lever at the same time swingingrearwardly by gravity to its limit or stop Z the result being to breakthe electric circuit of the door-lock. The current then passes via thecircuit-wires 1" and 7' and through the magnet-coil 0, therebyenergizing the latter and breaking the mercury-contacts by causing therod 0, &c., to rise to the limit of movement. The result of this actionis to cause the pins 0 of the controller-circuit to be withdrawn fromthe mercury in advance of the longer pins of the brake-circuit, thusinsuring that the controller circuit is dead before the brake mechanismis released by opening the brake-circuit, as hereinbefore stated.

I make no claim to an electric elevator system substantially asindicated in Fig. 8 of the drawings, except as being electricallyconnected with the master-switch A. and doorlock devices. In carryingout the invention I prefer to provide said switch with a series ofhand-controlled circuit-breakers or cut-out switches s, s, s, .5 and 8*,arranged substantially as represented in the drawings. The switches s sare kept normally closed, and when closed they are connected to the comductors w of the door-lock circuit. They are at all times connected toconductors 0", communicating with the magnet-coil of the master-switch.The normally open switch .9 is connected by conductors if 2- to themagnetic device 4, which constitutes a part of the brakecontrollingmechanism of the elevator. Said conductors are further connected to thetwo mercury-cups a a and to a resistance-coil E. This latter is ahigh-resistance shunt, adapted to carry any excessive increase ofvoltage in the circuits connected therewith. The normally open switch sis connected by conductors u u to the controller-circuit, through whichcircuit passes the current for manually controlling the operation of thecar. Said conductors also lead to the other pair of mercury-cups (Z (n.The other or bottom switch 8" is normally open. It is connected byconductors r' 7'-| to the main supply-circuit and also to saidconductors r 1" of the door-lock circuit. As thus arranged it is clearthat when it is desired to disconnect or cut out the door-lock circuitfrom the master-switch it is readily effected by opening switches .9 s,and by closing switch 8 the master-switch is cut out altogether.

It is to be understood that when the pins (1 of the conductor-bars a anda are in contact with the mercury contained in the respective cups thecorresponding circuits employing the conductors t t and a a are therebyclosed.

Fig. 10 represents my improved masterswitch A and system arranged foruse in the class of electric elevators in which the motors movementscease whenever the car stops. In this case the master-switch isinterposed between the motor and a main circuit-breaker T, connectedwith the conductors P P of the power-circuit. The mercury-cups a a andcorresponding conducting-bar connect, say, with the main wire P, theother mercury-cups a a and bar a being connected with the fellowconductor P. As drawn the several switches s s s s are kept normallyclosed, while a is normally open. The switches and s are in direct andcontinuous connection with the main circuit by means of conductors n12?, respectively. From the switch 8 a conductor n" connects with aresistance E, and from the latter the current passes to switches s and sand magnet-coil 0 by means of con ductors 12 One of the conductors '1'of the door-lock circuit is also connected with switch 8. From theswitch .9 a conductor a connects with the switch 3 and also with saidcoil 0 and switch 8, the latter being connected with the other conductor9' of the door-lock circuit. Now whenever the elevator is workingnormally the electric current flows from the conductors of thepower-circuit through the then closed master-switch to actuate themotor, some of the current at the same time passing via conductors n a an a and the said manually-controlled switches s 8' s s to the conductorsr r of the normally closed door-lock circuit. The act of opening alanding-door (Z breaks the circuit, thus short-circuiting the currentthrough the magnet-coil 0, thereby energizing the latter and opening themasterswitch by withdrawing the contact-pins from the mercury, the motorthen stopping. The stationary resistance-shunt E is employed to regulatethe amount of current used in the magnet-circuit.

It is obvious that various changes may be made in my improved system forautomatically controlling an electric safety device for elevatorswithout departing from the essential features embodied therein, andtherefore I desire to cover in this present invention such equivalentchanges or modifications.

I claim as my invention and desire to secure by United States LettersPatent* 1. The herein-described system for automatically controlling anelectric safety device for elevators, the same consisting of asuitablylocated and normally closed master switch electrically connectedwith the circuits controlling the movements of the elevator-car,

said switch having a magnet-coil of high resistance shunt-connected tothe mam powe i-. -I

ically controlling an electric safety device for v elevators, the sameembodying a normally closed master-switch shunt-connected to the brakeand controller circuits of the elevatorcar, a magnet-coil of highresistance electrically connected with the power-circuit and forming apart of said switch, and a series of normally closed door-locks locatedin an electric circuit connected to said master-switch, whereby upon'energizing said magnet-coil of the switch the latter operates to openthe said brake-circuit in advance of the controller-circuit.

3. In an automatic electric safety device for elevators, thecombination, in a master-switch of the class described, of a pluralityof independent conductor members, as a (0 provided with contact-pins innormal engagement with mercury cups electrically connected v withcircuits controlling the movements of the electric car, the pins of oneof said conductor members being longer than those of the other, and amagnet-coil provided with a vertically-movable core having saidswitch-conductors secured thereto and capable of moving upwardlytherewith to open the circuits whenever the coil is sufficientlyenergized, substantially as described.

4:. In an automatic electric safety device for elevators, a normallyclosed electrically-connected door-lock circuit having a comparativelylow resistance, normally closed electric circuits for controlling themovements of the elevator-car, and a master-switch provided with amagnet-coil of high resistance having a vertically-movable core membercarrying contacts in normal electrical engagement with saidcontroller-circuits, whereby the act of opening said door-lock circuitenergizes the magnet-coil to elevate its core thus at the same timeautomatically opening the car-controller circuits, substantially asdescribed.

5. In a system for automatically controlling the movements of anelectric safety device for elevators, a master switch provided withnormally closed mercury-contacts electrically connected with circuitsthrough which the movements of the elevator-car are controlled, adoor-lock circuit of low resistance electrically connected with thepower-circuit which supplies the current for operating said car, amagnet-coil of high resistance in continuous electrical connection withsaid door-lock and power-circuits, and a movable core for saidmagnet-coil capable of automatically breaking said mercury-contactswhenever the coil is energized by opening the door-lock circuit,substantially as hereinbefore described.

6. In a system for automatically controlling the movements of anelectric safety device for elevators, a master-switch electricallyconnected with a door-lock circuit having a low resistance and with thepower and car-controlling circuits, an electrically-connected magnetcoilof high resistance forming a part of said switch capable of beingenergized whenever the door lock circuit is broken, thereby through themedium of said coil opening the Said car-controlling circuits,substantially as described.

7. In a system for automatically controlling the movements of anelectric safety device for elevators, a master-switch interposed betweenthe door-lock circuit and car-controlling circuits and beingelectrically connected therewith, and having a plurality ofmanually-controlled cut-outs connected with said circuits, whereby theelevators movements may be controlled independently of the door-lockcircuit and master-switch, substantially as described.

8. The combination, in a master-switch, of mercury-contacts adapted tobe interposed in circuits through which the current passes forcontrolling the movements of an electric elevator, a suitably-arrangedmagnet-coil of high resistance, a low-resistance shunt electricallyconnected with said magnet-coil, and a vertically-movable rod or corecarrying conductors in normal engagement with the mercury but capable ofbeing withdrawn therefrom automatically upon energizing the magnet-coil,substantially as described.

9. The combination of two pairs of electrically-connected insulatedmercury-cups, a pair of insulated conductors provided with contact-pinsin normal engagement with said cups, an electrically-connectedstationary magnet-coil of high resistance, a movable core or rod passingthrough the center of said coil having said pin-carrying conductorssecured to its lower end, and manually-controlled cutouts or subsidiaryswitches arranged to be located in electric circuits which energize saidcoil, substantially as described.

10. In an electric safety device for elevators, a master-switchelectrically connected with circuits through which the movements of theelevator are controlled and provided with a magnet-coil of highresistance adapted when energized to actuate the switch and open saidcircuits, thus rendering the car inoperative, a door-lock device locatedin an electric circuit connected with the magnet-coil, said device beingprovided with insulated yielding conductor members, and a movablecontact member adapted when the door is closed to engage said yieldingconductors and form a short-circuit therewith, whereby the door-lockcircuit is closed and the magnet-coil of the master-switch demagnetizcd,substantially as described.

Signed at Providence, Rhode Island, this 8th day of May, 1903.

HARRY G. WRIGHT.

Vitnesses:

Geo. H. REMINGTON, G. E. SMITH.

